Enzymes and Their Functions

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Questions and Answers

What happens to enzyme function when the pH is significantly lower or higher than the optimum pH?

Enzymatic function is lost due to disrupted tertiary structure. (correct)

Tertiary structure is maintained.

Enzymes exhibit increased substrate binding.

Enzymes become more effective.

Which enzyme has the highest optimum pH for its activity?

Trypsin

Pepsin

Sucrase

Arginase (correct)

What effect does increasing enzyme concentration have on the rate of reaction?

It has no effect on the rate of reaction.

It only increases the rate of reaction if substrate concentration is also increased.

It increases the rate of reaction until substrate saturation occurs. (correct)

It decreases the rate of reaction.

What is the role of the end product in feedback control of metabolic pathways?

It acts as a negative regulator to inhibit the first enzyme. Signup and view all the answers

Which of the following statements is true about zymogens?

They must be activated to function as enzymes. Signup and view all the answers

What role do enzymes play in biological reactions?

They act as biological catalysts. Signup and view all the answers

What is the active site of an enzyme?

The region where the substrate interacts. Signup and view all the answers

Which model describes the flexibility of the active site adapting to the substrate?

Induced-fit model. Signup and view all the answers

Which of the following factors does NOT affect enzyme activity?

Color of the enzyme. Signup and view all the answers

What happens to enzymes at high temperatures?

They lose activity due to denaturation. Signup and view all the answers

What is the result of the enzyme-substrate complex formation?

The substrate is converted into products. Signup and view all the answers

What is a common naming convention for enzymes?

Enzymes typically end with 'ase'. Signup and view all the answers

Which statement is true regarding the lock-and-key model of enzyme action?

It emphasizes specificity between one enzyme and one substrate. Signup and view all the answers

Which of the following zymogens is activated in the stomach?

Pepsinogen Signup and view all the answers

What is the function of a kinase in enzyme regulation?

Activates enzymes by phosphorylation. Signup and view all the answers

Which enzyme is activated from its zymogen form proinsulin?

Insulin Signup and view all the answers

Which of the following statements regarding cofactors is true?

Metal ions can serve as cofactors for enzyme activity. Signup and view all the answers

What type of molecule is a coenzyme?

Small organic molecule Signup and view all the answers

How are fibrinogen and prothrombin activated?

Both are activated in damaged tissues. Signup and view all the answers

What is the main role of vitamins in the body?

They are essential for normal health and growth in trace amounts. Signup and view all the answers

What is the role of a phosphatase in enzyme regulation?

It inactivates enzymes by removing a phosphate group. Signup and view all the answers

Study Notes

Enzymes and Enzyme Action

Enzymes are biological catalysts
Increase the rate of a reaction
Remain unchanged during the reaction
Allow for faster conversion of reactants to products

Enzymes and Active Sites

Active site is where the substrate fits for reactions to occur
Substrate (e.g., lactose) is held in place by hydrogen bonds with amino acid R groups of the enzyme (e.g., lactase)
Amino acids within the active site are crucial

Enzyme-Substrate Complex

Active site of lactase is flexible to accommodate the substrate
The reaction complex is complete when the disaccharide is hydrolyzed
Monosaccharide products are released from the enzyme
The enzyme is ready to bind another lactose molecule

Models of Enzyme Action

Lock-and-key model: One enzyme fits one substrate
Induced-fit model: More dynamic, flexible active site adapts to substrate shape to assist product formation and lower the activation energy, this is a more modern view of enzyme action.

Learning Check

Active site is a section of the enzyme.
In the induced-fit model, the enzyme's shape changes to fit the substrate.

Names of Enzymes

Enzyme names typically end in -ase
Enzyme names may indicate the reacting substance (e.g., sucrase for sucrose)
Enzyme names may reflect the function (e.g., oxidases for oxidation)
Common names for digestive enzymes exist (e.g., pepsin and trypsin)

Factors Affecting Enzyme Activity

Enzyme activity is the speed of reaction catalysis
Activity is heavily influenced by factors like temperature, pH and enzyme and substrate concentration

Enzyme Activity and Temperature

Enzymes show peak activity at an optimum temperature.
Low temperatures result in low enzymatic activity
High temperatures cause denaturation and loss of activity

Enzyme Activity and pH

Enzymes function best at an optimal pH.
pH variations affect amino acid charges, impacting enzyme effectiveness
Extreme pH values can disrupt the enzyme's tertiary structure and cause loss of function

Optimum pH values

Enzymes in different organs (e.g., stomach, small intestine, liver) operate at specific pH values.
Specific enzymes in the table are associated with their optimal pH values and their locations.

Enzyme Concentration

Increasing enzyme concentration (at constant substrate concentration) increases the reaction rate
More substrate binding to the enzyme occurs

Substrate Concentration

Increasing substrate concentration (at constant enzyme concentration) increases the reaction rate.
Enzyme eventually becomes saturated with substrate, reaching maximum activity

Feedback Control: Metabolism When Needed

End product of a series of reactions acts as a negative regulator for the initial enzyme, stopping the reaction chain
This process stops until the end product is no longer present to bind to the initial enzyme, then the reaction process restarts.

Zymogens: Proenzymes

Large, inactive enzyme precursors are produced, activated when needed
Examples include pepsinogen, trypsinogen, and others.
The enzymes are produced in one location and then activated in another.

Enzyme Activity Regulation

Kinase activates an inactive enzyme by adding a phosphate group (phosphorylation)
Phosphatase activates an inactive enzyme by removing a phosphate group

Enzyme Cofactors

Simple enzymes: Contain only protein
Many enzymes require cofactors.
Cofactors are small molecules such as metal ions or coenzymes.
Coenzymes are organic molecules, often vitamins, that assist in enzyme function
Table 20.9 shows enzymes that require metal ion cofactors.

Vitamins and Coenzymes

Vitamins are organic molecules essential for health and growth
Vitamins are needed in trace amounts

Water-Soluble Vitamins (B, C, H)

Must be regularly replenished
Not stored in the body, excess excreted
Function as cofactors for enzymes
Can be destroyed by heat (boiling)

Fat-Soluble Vitamins (A, D, E, K)

Stored in the body
Involved in vision, bone formation, antioxidants, and blood clotting.
Not coenzymes for catalytic reactions

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Description

This quiz explores the key concepts related to enzymes, including their role as biological catalysts, structure, and the mechanisms of enzyme action. It covers important topics such as enzyme-substrate complexes and models of enzyme action. Test your knowledge on how enzymes facilitate chemical reactions and the significance of active sites.